TOKYO/SEOUL - Japan is sticking to its position on a deal with South Korea concerning Korean women forced to work in Japan’s wartime military brothels as so-called comfort women, a government source said Thursday, even after South Korean President Moon Jae-in called the deal “flawed.”

Tokyo’s “position of seeking the steady implementation of the agreement is unchanging,” the source said, suggesting it does not plan to agree to any further demands Seoul might make in the wake of a report released Wednesday that said the South Korean government failed to gather adequately the opinions of the former comfort women before reaching a deal with Japan in 2015 intended to address the issue.

The Japanese government said through diplomatic channels that there is “no other option but to uphold the agreement.”

On Thursday, Moon said the country’s 2015 agreement with Japan to settle a decades-long impasse over the comfort women is seriously flawed.

Moon’s statement — in which he vows unspecified follow-up measures to meet the victims’ demands — potentially throws the future of the deal into doubt, two years after both countries declared it “final and irreversible.”

Moon has directed his government to compile a new policy on the issue. But a high-level official at the presidential office indicated that a decision is likely to be made early next month after hearing the opinions of the victims.

The statement came a day after a state-appointed panel concluded that Seoul’s previous conservative government had failed to properly communicate with the victims before reaching the deal.

The panel also said parts of the deal had not been made public, including Japanese demands that the South Korean government avoid using the term “sexual slavery” and provide a specific plan to remove a bronze statue representing the comfort women in front of the Japanese Embassy in Seoul. South Korea in response said it will formally refer to the victims as “victims of Japanese military comfort stations” but didn’t make any clear promise about the statue, according to the panel.

“It has been confirmed that the 2015 comfort women negotiations between South Korea had serious flaws, both in process and content,” Moon said in a statement read out by his spokesman.

“Despite the burden of the past agreement being a formal promise between governments that was ratified by the leaders of both countries, I, as president and with the Korean people, once again firmly state that this agreement does not resolve the issue over comfort women.”

While his comments seem to suggest that Seoul may seek a renegotiation of the deal, something that is sure to anger Tokyo, Moon also said that the issues over history should not affect efforts to build “future-oriented relations” between the countries.

Some experts see it as unlikely that Moon’s government will spark a full-blown diplomatic row with Japan by scrapping the deal when the allies face pressing needs to form a strong united front against North Korea’s growing nuclear threat.

“If we get to the point where the South Korean government demands (we) revise the agreement, we’ll be (in a situation) where countries can’t keep their promises to one another,” a senior Japanese official said.

Foreign Minister Taro Kono said Wednesday that Japan sees “no problem in the process” that led to the agreement, and warned that bilateral relations will “become unmanageable” if South Korea seeks to review it based on the report.

But bilateral coordination remains essential in dealing with the security threat from North Korea’s development of nuclear and ballistic missiles.

“It’s important for both sides to make efforts to build a friendly relationship as neighbors,” another Japanese government source said.

Under the deal, Japan had agreed to provide ¥1 billion ($8.8 million) in cash payments to the dwindling number of surviving victims, while South Korea had said it would try to resolve Japanese grievances over the statue in front of the embassy.

The deal came under heavy criticism in South Korea where many thought the government had settled for much too little. Japan has been angry that South Korea hasn’t taken specific steps to remove the statue and similar monuments in other places around the country, insisting there had been a clear understanding to do so.

The deal was negotiated under Moon’s conservative predecessor, Park Geun-hye, who was ousted from office and arrested in March over a corruption scandal. Moon vowed to redo the deal during his presidential campaign, but has so far avoided specific discussion of any renegotiation since taking office in May.